Hydroxyethylcellulose cryogels used for entrapment of Saccharomyces cerevisiae cells

Cryogels of cellulose ether, hydroxyethylcellulose (HEC), were obtained via UV-irradiation of moderately frozen aqueous solutions in the presence of water soluble photoinitiator, (4-benzoylbenzyl) trimethylammoniumchloride (BBTMAC). The suitability of the cryogels as matrices for immobilization was studied by entrapment of Saccharomyces cerevisiae cells. The cryogels were characterized by measuring their rheological parameters, gel fraction yield and the degree of equilibrium swelling. The cells entrapped inside the matrix acted as pore fillers and strengthened the cryogels, while glucose incorporated into the gel had the opposite effect. The applicability of the immobilized systems was investigated by performing batch ethanol production from glucose. The operational stability of the gels was tested in batch fermentation with three cycles. The storage stability was investigated in seven repeated batches after 6 months storage of lyophilized cryogels in distilled water. The ethanol production ranged from 70% to 95% of the theoretical yield for the gels with 15% cells, and from 87% to 95% for the gels with 25% cells.